Washington: Using bundles of vertical zinc oxide nanowires, researchers have fabricated arrays of piezotronic transistors capable of converting mechanical motion directly into electronic controlling signals.
The arrays could help give robots a more adaptive sense of touch, provide better security in handwritten signatures and offer new ways for humans to interact with electronic devices.
The arrays include more than 8,000 functioning piezotronic transistors, each of which can independently produce an electronic controlling signal when placed under mechanical strain.
These touch-sensitive transistors - dubbed "taxels" - could provide significant improvements in resolution, sensitivity and active/adaptive operations compared to existing techniques for tactile sensing. Their sensitivity is comparable to that of a human fingertip.
The vertically-aligned taxels operate with two-terminal transistors. Instead of a third gate terminal used by conventional transistors to control the flow of current passing through them, taxels control the current with a technique called "strain-gating."
Strain-gating based on the piezotronic effect uses the electrical charges generated at the Schottky contact interface by the piezoelectric effect when the nanowires are placed under strain by the application of mechanical force.
"Any mechanical motion, such as the movement of arms or the fingers of a robot, could be translated to control signals. This could make artificial skin smarter and more like the human skin. It would allow the skin to feel activity on the surface," explained Zhong Lin Wang, a Regents` professor and Hightower Chair in the School of Materials Science and Engineering at the Georgia Institute of Technology.
Future work will include producing the taxel arrays from single nanowires instead of bundles, and integrating the arrays onto CMOS silicon devices. Using single wires could improve the sensitivity of the arrays by at least three orders of magnitude, Wang said.
"This is a fundamentally new technology that allows us to control electronic devices directly using mechanical agitation. This could be used in a broad range of areas, including robotics, MEMS, human-computer interfaces and other areas that involve mechanical deformation," Wang added.
The research was reported in the journal Science online.